Airplane control



May 5, 1931. R. CHILTON 1,803,493

- AIRPLANE CONTROL Filed April 18, 1929 2 Sheets-Sheet 1 W ATTORN' May 5, 1931. cHlLTON 1,803,498

AIRPLANE CONTROL Filed April 18, 1929 2 Sheets-Sheet 2 IN VEN TOR Razz/v.0 67w; 70/1 '1' BX) M I, f ATTORNEY Patented May 5, 1931 UNITED STATES" PATENT OFFICE ROLAND CHILTON, 0F KEYPORT, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO I AEROMARIN E PLANE & MOTOR COMPANY,

PORATION OF NEW YORK Application filed April 18,

This inventionrelates to airplane controls,

and in a specific aspect to lateral or aileron control means. A prime object of the invention 1s to provide a new organization of control mechanism and movable control surfaces which shall maintain effective control at and beyond the stall.

As is well known in the art, the lift of an alrfoil increases with an increase of the angle of attack up to a critical angle identified with the burble point whereat the streamhne flow over the wing breaks down and a sudden loss of lift occurs causing an actual drop of the airfoil in flight; and unless this resulting drop is, fortuitously equal on the right and left hand wings, the well known spin, which is regarded as the most prevalent danger in flying, results. This auto-rotation follows from the facts that; beyond the stall, the wing having the greater angle of attack has the least lift and that the faster falling wing has in effect agreater angle of attack than the other. The faster falling wing having the least lift-obviously results in a tendency towards increased rotation.

It must be kept in mind that the angle of attack is and the actual line of travel of the alrplane, which last, at the stall, will be steeply downwards although the nose of the machine is steeply above the horizon.

Conventional ailerons comprise hinged flaps at the trailing edge of the wings connected for opposite displacement by lateral movement of the control stick; the mean angle of the right and left hand ailerons being always that of the wing, wherefrom it results that when the wing is stalled the aileron also loses effective lift (negative lift in the case of the upturned aileron) and such lateral control means are accordingly ineffective at or after the stall. Thus lateral control is lost and the pilot is unable to correct an incidental excess drop in one wing which initiates the turning which develops into auto-rotation by the resulting difference in lift between the faster and slower droppingwings. The only remedy in present machines is to first cure the stall by nosing down the ship to regain flying speed in order to the angle between the win chord IN 0., OF KEYPORT, NEW JERSEY, A COR- AIRPLANE CONTROL 1929. Serial No. 356,128.

bring the angle between the wing and the load, i. e. the air reactions thereon are downward so that a stall results in a loss of positive lift in the wings and of negative lift in the tail whereby the nose goes down and the tail up; the resulting dive restoring flying speed automatically if auto-rotation has not intervened and set up a gyroscopic couple which keeps the nose up. This dive and recovery, however, absorbs a few hundred feet of altitude and hence the. crashes that follow stalls at low altitude. These dangers may be avoided by so arranging the ailerons that they remain unstalled after the wings have reached the burble point, and a price object of the invention is to provide simple and effective means whereby this may be realized in practice.

Ithas been proposed to dispose the ailerons away from the. trailing edge of the wing so that they may work in air undisturbed by the stalled wing, but this alone does not prevent the ailerons themselves from stalling with the wings because both participate in the pitching movement of the whole ship (with conventional controls) so that both (the ailerons and the wing) have the same mean angle of incidence, any difference in angle between the separate ailerons merely resulting in the one at the greater angle of incidence being worse stalled.

The present invention on the contrary provides a novel and simple control system wherein the ailerons do not follow the pitching movement of the airplane but are floated to always align their mean angle to the direction of movement of the ship thru the air, only the angle between the ailerons bein determined by the pilots control, in opposition to the conventional arrangement wherein the mean angle of the two ailerons is fixed at or near parallelism with the wing chord.

- The ailerons in the present invention accordingl are floated pivotally ahead of their center Q pressure so as to possess weather vane stability whereby they are free in flight to aligntheir mean angle to the flight path even tho this path be at a great angle to the wing chord (as in a stall) and the angle'between the ailerons only is controlled.

The mechanism is so arranged that the automatic unitary movement of the two ailerons relative to the airplane as a whole (which may occur withoutchange in the angle between the ailerons) results in a vertical movement of the control stick gri whereby the pilot may feel the altitude o the ailerons, which i will give him an index of the actual angle additional to the avoidance and correction of spins as follows It is well known 'that the slowest landing (and, therefore, the most desirable as regards constricted or rough landing areas) is that made at a complete stall whereat the actual path of travel of the airplane is much steeper than in the normal glide, even tho the nose of the ship be held relatively high, a condition described by pilots as squashing. Except in ships of exceptional inherent lateral sta-- bility and in steady air conditions, this squashing cannot safely be initiated except very close to the ound because of the danger of one wing ropping resulting in slipping in which, from a substantial height, in-

volves a crash landing on one wing. However,v the relatively steep path 0 descent whilesquashing is of great advantage in clearing an obstacle for landing in a restricted area beyond, and*is a method successfully used for obtaining slow and short landings by pilots having suflicient assuranee that they can maintain the ship accurately in the very narrow range of, altitude between squash ing and stalling. The ordinary pilot with the present aileron controls is usually welladvised in avoidingthis method. It is one object of. the present invention to enable a ship to be flown indefinitely at the stall with safety in the hands of a relatively inexperienced pilot sothat he may be able to make a short and slow approach'in order tosuccessfully negotiate anemerg'ency landing in a tight field.

The'foregoing advantages of floating ailerons diflerentially controlled are conceded b many of those skilled in the art (of theoretical aerodynamics) but-great mechanical difliculty and complication in such control systems as have usually alleged as the reason that these advantages have not been reduced to practice.

The prime object of the present invention is to provide a simple and direct control system, readily applicable to conventional airplanes, which will permit the desired auto matic alignment of the mean angle of the two ailerons with the actual flight ath, whilst maintaining effective control 0 the angle between the ailerons. A further object consists 1n introducing an additional movement to the control stick (in this instance a vertical movement) proportional to the mean angle of the two ailerons to the wing chord, whereby the pilot may feel the automatic changes in this angle which will be an index of the actual instantaneous angle of attack and whereby he may further, by opposing or assisting such movement, be provided with an additional control movement eflective longitudinally (or in .pitch); A still further object is to achieve the foregoing without changing the normal control movements from those which have become the standard familiar to all pilots.

For convenience of explanation the word stick has been used to designate the control member manipulated by the pilot but it will be obvious that the provisions of this invention are equally applicable to a wheel or other type of control member.

Various other objects andad-vantages of the invention will be in part obvious from an inspection of the accompanying drawings and a careful consideration of the following particular description and claims ofone form of mechanism embodying my invention.

In the drawings:

Fig. 1 is a perspective diagrammatic View of an airplane equipped with the aileron control of this invention.

Fig. 2 is aperspective view on a larger scale showing the control mechanism.

Referring to Fig.1 a low wing monoplane having wing tip type ailerons 10 and 11 is indicated, but it will be understoodthat the invention is applicable to any type of wing arrangement. The wings 12 and 13 are equipped with aileron shafts 14 and 15 extending from the ends of the wings and about which the ailerons 10 and 11 are arranged to pivot. shown in enlarged view in Fig.2, are a pair of rockin shafts 16 and 17 and these are respectively connected by any suitable means so as to partake of the motion of and transmitmotion to the ailerons. The connecting means illustrated comprise rocking levers 18 een previously proposed is Near the center line of the ship, as

and 19 secured to the ends'of the shafts 16 secured to the ailerons; the levers being connected biv cables 22 and 23 brought over suitable pul eys 24 and 25. Secured to the rocking shafts 16 and 17 are approximately horizontal levers 26 and 27 control stick 30is mounted for rocking motion with a longitudinal shaft 31, the connection being pivotal for fore and aft of the stick which istransmitted to the-longitudinal control surfaces 32 of the tail by an suitable means such as the rod 33 and'the levers 34 and cables 35. Slidable upon the stick 30 is an outer tube 36 having a grip 37 and equipped at its lower end with a rigid cross head 38 termlnating in the eyes 40 and 41 on respective sides above the extended ends of the levers 26 and 27. These are engaged by the links 42 and 43 so that the effect of locking the control stick laterally is to raise one lever and depress the other. The ailerons partake of this motion b means of the cable connections previously described.

It will be seen that on account of the vertical freedom of the outer tube 36 with the I grip 37, the controllevers 26 and 27 are free to rise and fall vertical in a unitary manner and that such unitary motion (without a change in angle between the levers or the connected ailerons) is free to occur when the stick is maintained vertical in which condition no change of relative angle between the ailerons is possible. At the same time when the stick is held over to one side a corresponding difference in the angle between the ailerons is enforced without, however, enforcing any specific mean angle of the ailerons til) relative to the ship as a whole. Thus the ailerons at all times are free to align themselves with the actual flight path of the ship whereby they will remain unstalled, even though the wing bebrought past the stalled position. To insure the automatic alignment of the ailerons with the air stream, the aileron mounting shafts 14 and 15 are disposed ahead of the center ofpressure of the aileron surface whereby the aileron possesses weather-vane stability.

It will be seen that as the ailerons together change their angle, (from change in the relative direction of the air stream over the wing) they will impart a vertical movement to the floating outer tubeof the stick1-'fwh ich will be felt by the pilot and may, in fact, be in a certain degree initiated or resisted by him which will give him a longitudinal control auxiliary to the normal control afforded by the horizontal movable tail surfaces, which latterwill be responsive to fore and aftmovement of the stick in the usual way.

The ends 40 and 4-1 of the cross lever 38 which is rigid with the floating tube 36 are preferably disposed at about the same horizontal levelas the shaft 31 which forms the rocking axis of the stic,k? so that little or and a conventional no side motion of the tops of the links 42 and 43 occur.

- It will be see'n'that with a relatively slight mechanical addition to the conventional control arrangement differential control for floating ailerons is provided.

Variations may be resorted to within the scope of the invention and portions of the improvements may be used without the y others, whilst not departing from the spirit of the invention.

Having thus described my invention, I claim: 1. The. combination W including,

control means including a rockable control member, a tube slidable' on said member and having a hand grip, and a two-arm cross head rigid with said tube and operatively connected to the respective ailerons.

2. In an airplane in combination, a pair of pivotally mounted ailerons connected so as to be together free for self-alignment with the flightpath of the airplane, and control means havlng free vertical movement affording said freedom and adapted to control the relative angle of the two-ailerons responsively tolateral movement ofthe control means. 1

3. In an airplane in combination, a pair of ailerons, a control member connected thereto to enforce opposite angular movement of the ailerons when the control member is rocked, said control-member being floated vertically to permit free unitary movement of the two ailerons.

4. The combination with an airplane, of a pair of ailerons freely pivotally mounted for automatic unitaryangular movement responsive to changes in attitude of the airplane, and

control means floated vertically to afford said freedom and adapted'when moved laterally to move the ailerons simultaneously and in opposite directions.

nation of, a pair of floatingly pivoted ailerons, a rockable control means having unrestrained vertical movement and adapted when held against rocking to restrict the ailerons to unitary movement and when rocked to move the ailerons in opposite directions.

6. A control system for actuating airplane ailerons from a rockable control member including in combination, levers connected to respective ailerons, a cross-head rigid angularly with the control member and freely 5. In an airplane control system, thecombi- I slidably mounted thereon, a hand grip slidable with said cross-head, and connecting means between the ends of said cross-head and the respective levers.

7. In an airplane having. a control stick rockably mounted on a horizontal shaft, in

combination, a pair of ailerons pivotally mounted, levers pivotally mounted on each s ide of said shaft and connected so as tocontrol respective ailerons, a cross-head mounted for rocking motion with said stick and at all '10 times freely slidable thereonand connected to control the angular relation'of said levers.

' 8. Inan airplane havingapivotally mount-" ed control member in combination, aileron control means on each side of said pivot, a

' cross-head angularly rigid with the control member and at all times freely slidable thereon, ahand grip rigid with said cross-head,

and means adapted to connect each end of said cross-head to the respective aileron control means. I

9. In a system for actuating the control surfaces such as'ailerons in'an airplane, the combination of a pair of control surfaces, a control stick mounted for rocking movement, an

o crating member mounted for automatic sl ding longitudinally thereon and provided with rigid laterally extending arms, a pair of J lay shafts disposed one on either side of said control stick and having levers connected with the above said arms for movement of the shafts thereby respectively, said control surfaces being operatively connected to said .shafts' Signed at Keyport, ihthe county of Monl mouth, and State of New Jersey this 15th day of April, 1929. I J (ROLAND CHILTON. 

